Arataki, the Malayan sun bear, turned 25 this week, with zoo staff setting up enrichment activities for the birthday boy. This included a four-tier birthday cake with pumpkin, grape and avocado as well as nuts and Weetabix.

Zoo keeper Jemma Walsh said this was "a pretty big milestone for us at the zoo"

"We're really, really loving the crowds coming out to support Arataki as he turns 25."

Ms Walsh said not much is known about sun bears and their life expectancy in the wild because they come from remote parts of the world, but in captivity 25 was classified "as an old bear".

"There have been some living up to about 30, but that would be quite rare," she said.

Born at New Zealand's Wellington Zoo, Arataki was brought over to Canberra at a young age to be company for Otay the sun bear, who was rescued from illegal trade by Australian wildlife conservation and animal welfare organisation Free the Bears.

Ms Walsh said in the wild, deforestation, climate change and illegal bile trade were among the biggest threats to the species.

"These guys unfortunately, they are taken a lot from the wild as cubs, whether that's for the illegal bile trade or bear paw soup trade," she said.

"It is still seen, unfortunately in a lot of those traditional medicines, as an important healing property or else they can be taken as circus [animals] as well."

Standing at around five feet, sun bears are world's smallest bear species.

Ms Walsh said the pair have done "amazing work" for their species, raising money and awareness for sun bears, which are classified as vulnerable.

"Arataki and Otay are a power team, they've raised a lot of money and taught a lot of people about sun bears over the years," she said.

Arataki's celebrations attracted a crowd on Wednesday, with visitors stopping by to watch and wish the bear a happy birthday.

Among them was a family visiting from Melbourne.

Frank Thomas, 9, said he enjoyed watching the bear opening his presents.

"He deserves it," he said.

"I think it's important that we acknowledge the bear because 25 years is a lot.

"I just think it really deserves its birthday."